Engineers Design Battery-Free Wireless Device

Since the onset of television, radio, and WiFi, we have been inundated with a vast array of RF signals, which allow us to listen to music, watch television, and stay connected to one another with our mobile devices.

Recently, Nickolay Lamm and colleague Dr. M. Browning Vogel were able to visualize the various signal patterns that make up WiFi transmissions and illustrate those using rather striking colors. Suffice it to say they are everywhere, covering just about every square foot of space in populated cities, and thanks to some ingenious engineers, can be utilized to provide another service besides communications and artwork. Those engineers, from the University of Washington, have developed a way to harness those signals to power communications devices without the need for batteries or other power sources.

University of Washington’s Ambient Backscatter device is equipped with an antenna that picks up broadcast signals from TV or cellular sources and converts them into hundreds of microwatts of electrical power. (Source: University of Washington)

Known as Ambient Backscatter, the device (or any device equipped with the technology) is equipped with an antenna that picks up broadcast signals from TV or cellular sources and converts them into hundreds of microwatts of electrical power. The device uses the newly acquired power to modify the signal taken and then transmits that signal with embedded code back to the source. Other devices outfitted with the technology can then receive the coded messages and respond accordingly, which is necessary if the Internet of Things (IoT) is to become mainstream.

The engineering team constructed the device using an antenna connected to a PCB board the size of a credit card. The cards were then outfitted with a single LED that lights up when the card receives a signal without an onboard or external power source.

In tests, the engineers found that two cards positioned only a few feet away could communicate with one another using a transmission source positioned over six miles away. The power conversion, however, was only sufficient to relay sensor information or text messages, which is still impressive.

The technology opens the door to a host of near future possibilities that could benefit from ambient backscatter transmissions, including embedding sensors into hard-to-reach areas where power is an issue, such as concrete or inside walls and other structures. As long as the device is able to acquire a signal they could be implemented everywhere.

When the Ambient Backscatter device puts itself into "hibernation mode," it will only take advantage of RF signals, which it stores on a capacitor, until it has enough power to complete the function desired. Mobile users, for instance, would still be able to send and receive text messages even though their devices are no longer charged. The possibilities are vast when it comes to device implementation, but the technology is still in its infancy. However, it’s only a matter of time before it will be refined enough to be able to be used for more than text messages and sensor data.

Cabe, the approach you mention is just the way RFID tags work. In the case of RFID a device, the reader, sends out a signal and, for passive RFID tags, the energy is used to power the tag and respond with the information. That is not to say that this is a great idea. As your article points out, in populated areas we are inundated with RF signals. Of course, the people who are against smart meters, for example, which often use WiFi, say that it is the meters that cause them medical problems. One of the types of energy we have in abundance in the air is WiFi signals. This research shows that there is a lot more than the meters energizing the environment around us.

I thought this technology sounded familiar...I wrote about it in September: http://www.designnews.com/author.asp?section_id=1386&doc_id=267327 But I think your story takes a slightly different approach and talks about some aspects of the technology I didn't cover, so it's still relevant!

I don't know if I'm against "Smart Meters", but I am against a meter which can remotely turn off my electricity when I don't want it off....

The usage monitoring part I'm fine with, but I don't want my house to become part of the Demand Response grid! I'm involved with Demand Response at work, and have no desire for it to come to my house. Especially if it's the result of poor government politics limiting our energy supply tactics!

Just not a local or onboard one. To say that these are "communications devices without the need for batteries or other power sources." is thus inaccurate, and misleading at best. Since they are powered by transmitter(s) located remotely the article should state "without the need for batteries or other local power source."

Chuck, yes, this technology has been used for a while. It is the basis for all "passive" RFID tags. There are active tags. The RFID device in my car that automatically pays tolls is one. I expect it is the speed and distance that are issues there. On the other hand, most tags are passive and many are "printed".

Jim_E: demand response is an important part of making the system more robust. On the other hand, the smart meter on your house can, in general, only be used to turn your whole house on or off. Of course that could be done by a guy in a truck with the old system.

Real demand response in the home requires that you put control devices on individual appliances to allow them to be turned on and off from a remote location. It might even be something you would want to do yourself. In addition, with pricing informaton available, you could optimize your electrical usage to minimize your costs. You make the choice. Pay more to get it done now, or wait until it is cheaper. What is your problem with that?

Let me ask another question. Which would you prefer, a full black out or having your air conditioner turned off for a couple of hours? I think you would prefer the later.

Your comment about government is also off base. As far as I am aware, most electricity in the United States is provided by investor owned utilities. These tend to do a fairly good job of keeping the lights on. Energy supply in the US is also not a problem on the electrical side. In fact, since we are becoming more efficient, rates are going up because the investor owned utilities must be able to recover their investment. Just think about it. Every appliance, computer, and other electrical device in your home is more efficient than the item it replaces.

naperlou, Demand Response with a smart meter could only turn your house all the way on or all the way off. That's what I'm against. My electricity rates are very reasonable and honestly it would take a large incentive from the power company for me to be willing to participate in demand response even on my air conditioning.

I'm actively involved in the Demand Response (and Synchronous Reserve) participation at a large industrial facility, so I'm well versed with the programs and the payments.

As for the government comment, I don't think that I'm off base at all. Executive orders from the top are reshaping the energy generation capability of our country in a negative way, causing many large coal fired generating stations to be shut down. And the hoops required to open or even keep open existing nuclear power plants are onerous. Not permitting these plants to operate is what is going to cause brownouts and blackouts, not me running my air conditioning in August.

I do agree that increased efficiency of consumer goods a great thing, but saving milliwatts only goes so far when we don't have enough power plants in operation.

There is a prevailing view that government == bad, and ceding any form of control to the government is therefore bad. This view often gets conflated with "anyone or anything that exerts some control on me is government".

It can be easily demonstrated that staggering the switch-on of domestic air-conditioners reduces the base-load of the grid by a significant amount - often enough to obviate bringing more generation on-line - all without a noticeable change in people's comfort level, in fact without any measurable temperature changes at all.

Rather than looking at this as some form of rationing, I think it is more akin to orderly queueing. If we have to serve everybody at exactly the same time, I need far more capacity than if I choose to serve only a few at a time.

This is above and beyond the possibilities for actual adjustments of home temperature (allowing AC two degrees hotter when you are not home for example - or heaven forfend - allowing ourselves to get a little hotter in the summer and a little cooler in the winter).

Replace "goverment" with "computer hackers"... "Demand Response / turn off" off a city or some customers and one can see potential for mischief. Wireless security must be baked into any system, especially when it supports life safety, like the electrical grid.

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